Isolated Azure Functions build is broken when using artifacts layout

[Original FT from DevDiv] (https://dev.azure.com/devdiv/DevDiv/_workitems/edit/2674575)
When Isolated Azure Functions projects are combined with artifacts layout the build is broken.

Create a solution with at least two Isolated Azure Functions projects.

Add Directory.Build.props that enables artifacts output.

Build the solution from command line:

dotnet build --artifacts-path

Build randomly fails with

Cannot open '_artifacts1\obj\WorkerExtensions\release\Microsoft.Azure.Functions.Worker.Extensions.dll' for writing -- The process cannot access the file '_artifacts1\obj\WorkerExtensions\release\Microsoft.Azure.Functions.Worker.Extensions.dll' because it is being used by another process.

The problem is due to WorkerExtensions.csproj projects generated by functions build process output to the same locations:

\bin\WorkerExtensions
\obj\WorkerExtensions

See attached [AzureFunctions.zip](https://aka.ms/dc/file?name=B9aefa48944ed4336b3d6363434925cb3639031765591768222_AzureFunctions.zip&tid=9aefa48944ed4336b3d6363434925cb3639031765591768222) sample solution.